100-watt fuel cell

ABSTRACT

A commercially useful and marketable fuel cell is described. The cell is capable of operating at ambient conditions of temperatures, pressure and the like for long periods of time. The complete cell includes one or more banks of individual cells, each cell including an anode, an air breathing catalytic cathode, and means for controlled feed of fuel and an aqueous electrolyte. The catalytic electrodes may be catalytic silver. A 100-watt commercial fuel cell is described.

[ 5] Feb. 13,1973

Emited States Patent Goldberger 100-WATTFUELCELL 3,378,406 4/1968Rosansky...............................136/86 [75] Inventor:Maxcoldbergerwappingcom 3,146,131 8/1964Lmdenetal........................136/86R [73] Assignee: CatalyticTechnology Corporation, Primary Examiner-Winston A. Douglas Manchester,Conn. Assistant Examiner-H. A. Feeley g 1970 Att0rneyRosen & Steinhilper[22] Filed:

[57] ABSTRACT A commercially useful and marketable fuel cell is [21]App]. No.: 63,070

[52] US. Cl. descl'ibed- The can is capable of operating at ambientconditions of temperatures, pressure and the like for long periods oftime. The complete cell includes one or more banks of individual cells,each cell including an anode, an air breathing catalytic cathode, andmeans for controlled feed of fuel and an aqueous elec- [51] Int.

[58] Field of [56] References Cited 1 UNITED STATES PATENTS trolyte. Thecatalytic electrodes may be catalytic silver. A lOO-watt commercial fuelcell is described.

3,126,302 3/1964 Drushella..........................,....136/863,328,204 6/1967 Grubb 4 Claims, 5 Drawing Figures Pmamin w 3,716,414

sum 10F Rosin & STEINHILBER PATENTED FEB 1 31973 SHEET 2 OF 3 lmsau aSIEINHILBER PATENTEDFEBI 3% 3,716,414

SHEET 30F 3 LN'VILYIORS MAX GOLDBERGER m Ensw & STEINHILPER IOO-WATTFUEL CELL BACKGROUND OF THE INVENTION In recent years, there hasdeveloped the new art of fuel cells in which an appropriate fuel iscatalytically decomposed in a cell which produces direct conversion fromchemical energy to electrical energy. In the development of this art,there have been two principal directions of activity. In the firstplace, there have been produced usable fuel cells operating with a fusedelectrolyte which necessarily means that the cell must operate at a veryhigh temperature. Naturally enough, the high temperature and extremelycorrosive fused electrolytes seriously limit the areas of utility forsuch cells.

In addition to the work with fused electrolyte type cells, there hasbeen experimental work with fuels and electrodes operable at ambienttemperatures. At the present time, however, there is not believed to bean existing fuel cell either commercially available or suitable forgeneral use as a source of power and capable of operating at ambientconditions.

One of the specific problems associated with the development of acommercial fuel cell has been the provision of a suitable fuel. It isdesirable to have a fuel which is readily available, which is useful ina liquid form and which can be catalytically decomposed in an aqueouselectrolyte. I-Iydrazine hydrateis such a fuel, but it is not believedthat hydrazine hydrate has previously been employed in a commercialcell.

GENERAL STATEMENT OF THE INVENTION It is, accordingly, an object of thisinvention to provide a new commercially useful fuel cell capable ofoperating with a liquid fuel in an aqueous electrolyte to produce areliable, long lasting source of electric power under a wide variety ofambient conditions such as those which may be encountered in cold or hotclimates and under many conditions throughout the world. These andnumerous other objectives of a commercially satisfactory fuel cell areaccomplished by the present invention as described in specification andclaims wherein:

FIG. 1 is'a top view, partially in section of a power pack according toone embodiment of the invention;

FIG. 2 is an exploded view of a double cell according to one embodimentof the invention;

FIG. 3 is an isometric view of a power pack comprising a double bank ofcells according to one embodiment of the invention;

FIG. 4 is a diagrammatic representation of a 100- watt fuel cellaccording to one form of the invention;

FIG. 5 is an exploded view of a cell according to another embodiment ofa cell.

In general, the present invention is a commercially useful fuel cellcomprising one or more banks of individual electrolyte cells havingtherein an anode, an air breathing catalytic cathode, means to supply anaqueous electrolyte to the cell, means to supply a liquid fuel to thecell and control means to maintain liquid volumes and concentrations inthe cell and to produce electric power at a desired voltage andamperage. The cell is operable with various liquid, water misciblefuels, and a preferred fuel is hydrazine hydrate (64 percent hydrazine;36 percent water) which can be added to a cell containing an aqueouselectrolyte and which operates effectively in the cell whensignificantly diluted in aqueous electrolyte.

DETAILED DESCRIPTION OF THE INVENTION In FIG. I is shown a power packgenerally designated 11 according to one embodiment of the invention.The power pack comprises a multiplicity of individual cells 12 mountedin a frame or holder including an electrode bracket 14 positioned ateach end of each bank of cells and held together by bars 15 extendingfrom bracket 14 at one end of the bank of cells to the second bracket 14at the opposite end, and securely mounted thereon. The cells areseparated from each other by spacers 16 integrally mounted on each cell.Covers or shields 17 are positioned above the banks of cells to protectelectrodes and connections from being splattered with contaminating orcorroding materials. Wires or electric leads 19 are mounted at each endof each bank of cells in the power pack to provide the appropriateelectrical connections to utilize electricity generated in the cell. Inthe apparatus illustrated, there are two banks of 14 cells each, adaptedto supply watts of output power at a peak output voltage of 28 volts anda working potential of about 12 volts.

In FIG. 2 is shown a double cell 12 according to one embodiment of thisinvention. The double cell comprises two cells blocks 21 positioned tohold anode electrodes 22 near the center thereof and cathode electrodes23 at the outside walls thereof. When mounted in a power pack asillustrated in FIG. 1, two cells are mounted as a pair or as a doublecell with the cathodes 23 at the opposite outside faces, and thesepairs'of cells are positioned with an air space between each pair sothat the cathode electrodes 23 are mounted with one surface facinginwardly to the cell and the other surface facing outwardly to the air.The anode electrode 22 has a pair of electrode leads or contacts 24extending upwardly therefrom and thecathode electrodes 23 have a pair ofcathode electrode leads or contacts 25 extending upwardly therefrom.

The cell block 21 comprises a frame having side walls 30, bottom walls31 and a top wall 32 surrounding a central opening 33 which is theelectrolyte chamber in theassembled cell. A pair of vertical holes 35extends through the top wall 32 near the ends of the electrolyte chamberand is adapted to receive the anode electrode leads when the anodeelectrode is in its operating position in the cell block. l-iollowedportions or openings in the top wall 32 extend about half way from thetop of the cell block to the electrolyte chamber and provide an overflowor feed reservoir 36 for electrolyte in the cell. A plurality ofchannels 37 positioned vertically in the upper wall between the feedreservoir and the electrolyte chamber allow fuel such as electrolytefuel or emitted gas to pass freely between the electrolyte chamber andthe feed reservoir. A channel or opening 39 is provided to permitprimary feed of electrolyte from a fuel source into the feed reservoir.

Surrounding the electrolyte chamber 33 is raised wall or shoulder 40defining a channel 42. The wall extends entirely around the opening 33providing corner seals and mounting shoulders by which the electrolytechamber is tightly sealed against leaks. At the cathode face of the cellis an inset shoulder 44 shaped and adapted to receive the cathodeelectrode 23 in such a way that the cathode electrode seals off theelectrolyte cell opening and itself forms an external wall of the cell.On the opposite side of the cell block is a support flange 45 flush withthe face of the cell block whereby an electrically inert and nonpolarwall member 46 may be placed against the face of the cell block and isheld in place to seal off this side of the cell. Above the electrolytecell 33 is a second feed reservoir 47 defined by wall 46 and a recessedportion of the cell block 21. An overflow opening 49 communicates with avertical groove 50 in the cell block, whereby overflow fluid from theelectrolyte cell can be drained away. A plurality of openings 51 extendtransversely through the upper wall 32 communicating between the firstfuel reservoir 36 and the second fuel reservoir 47. On the back side ofthe cell, not shown in FIG. 2, is a spacer 16 (see FIG. 1) such that adouble cell can be mounted in a cell bank with a controlled spacetherebetween.

To assemble the cell, the anode electrode 22 is placed within theopening 33 of the electrolyte cell with its electrode leads 24 extendingupwardly through holes 35 and projecting thereabove. The cathode 23 isfitted into its support opening at the cathode face of the cell block 21with its leads extending upwardly above the cell and spaced from theanode leads. A cell wall 46 or electrically inert wall member ispositioned at the opposite face of the cell to complete one cell unit.Desirably, two cell units are placed together with a single cell wall 46operating as the common back wall of both cells. When thus assembled,each cell has a cathode electrode positioned to form one cell wall withan air space on the outside and with the electrolyte chamber inside thecathode. An anode electrode 22 is positioned essentially in the middleof the electrolyte cell and a back wall 46 completes the sealing off ofthe cell. Upper feed reservoirs communicate with the electrolyte cell insuch a way as to feed the electrolytic liquid and fuel to the cell aswill be described hereinafter.

In FIG. 3 is illustrated an assembly comprising two banks of cellsrepresenting a power pack assembly for a lOO-watt fuel cell. Theassembly includes a plurality of cells 12 arranged in two banks 52representing a total of 28 cells which make up the l-watt fuel cell.Each bank of cells comprises 14 individual cells mounted in pairs witheach pair spaced apart by spacers 16. In each pair of cells there is acell block 21 back-to-back with a second cell block 21, with a commonwall 46 therebetween. In each cell is an anode electrode 22 and acathode electrode 23 which forms an outer wall of the cell, all asdescribed in connection with FIG. 2.

In each bank of cells, a fuel input line 53 is mounted to deliver aliquid fuel into feed reservoir 36 through an individual fuel nozzle 54operably mounted on fuel manifold 55. Similarly, at the base of thecells, is an overflow manifold 56 having a plurality of input nozzles 57which are plugged into the base of the vertical grooves or overflowtubes 50. A pump (see FIG. 4) is controlled to feed additional fuelthrough input line 53 to the cell and to convey overflow liquid to areservoir (see FIG. 4).

Projecting upwardly out of the individual fuel cells are the anodeelectrode leads 24 and the cathode electrode leads 25 positioned underthe protection of covers or shields 17. In the lOO-watt fuel cell unit,these anode and cathode leads are electrically series-connected so thatthe voltage output of the unit is equal to the sum of the voltageoutputs of the individual cells. In the unit as described with 28 cells,the total voltage output is controlled at 28 volts open circuit and 12volts under constant load at 10 amps constant current.

In FIG. 4 is illustrated in diagrammatic form an entire lOO-watt fuelcell according to one embodiment of the invention. According to thisembodiment of the invention, two banks of cells generally designated 12are positioned above a tray or fuel reservoir 61' positioned at the baseof the unit. A fuel level control device such as a float 62 operating avalve or other mechanism to introduce fuel from a fuel input line 64 ispositioned in the fuel reservoir and is adapted to maintain the level ofthe fuel in the reservoir at a suitable and convenient level. Moresophisticated means of fuel control, such as electronic control may beemployed, but were found unnecessary. A pump 65 is positioned in or nearthe fuel reservoir and is adapted to draw fuel through the pump inlettube 66 and circulate the fuel through a fuel conduit 67. According tothe embodiment shown, which has two banks of fuel cells, a Y connector69 spreads the flowing fuel into the individual fuel input lines 53where they are fed through nozzles 70 into the individual cells. Whenthe fuel cell is in operation, the fuel flows through the lines, is fedinto the cells through nozzles 70 and flows through overflow drain tubes56 and is thus returned to the tray or fuel reservoir 61. An internalfuel tank 72 may contain sufficient fuel for several hours of operationor, if desired, an external tank of large size such as for example, aSS-gallon drum of fuel may be employed.

Electrical controls (not shown) may be employed to control the currentflow or output voltage of the cell and there is indicated in FIG. 4 aprotected electric lead 74 leading from the fuel cell mechanism througha wall 75 of a cabinet enclosing the fuel cell to an external dial andcontrol knob 76 which may regulate voltage, turn the mechanism on andoff or otherwise control the mechanism of the fuel cell. The specificelectrical controls do not form part of the present invention.

In FIG. 5 is illustrated a fuel cell unit generally designated 80comprising a cathode cell frame 81 and an anode cell frame 82 on whichare positioned a cathode electrode 23, two anode electrodes 22 and aplastic cover 17. When assembled, this structure forms a fuel celladapted to be placed face to face with a second cell to form a fuel cellpair as in FIG. 2.

The anode cell frame 82 is divided by means of a vertical support member84 to receive two anode electrodes 22. These anode electrodes 22 arefitted against the face of the cathode cell frame which is positionedagainst the cathode cell. The vertical support member 84 is recessed sothat a single supply of anode cell fluid circulates to be in contactwith both of the anode electrodes 22. Openings in the anode cell frameare adapted to receive the anode electrode and to present anode cellfluid such as a fuel at one side of the anode electrode surface. Mountedon the anode cell frame above the openings is a guide and fuel director85 which serves several purposes. First, it forms a spacer for theplastic cover 17. Second, it is positioned directly below fuel inlet 86and slanted away from fuel overflow opening 49, whereby fuel enteringthrough fuel inlet 86 is caused to circulate counterclockwise (as shownin FIG. 5) through the fuel cell and then out through the overflowopening after it has circulated through both halves of the anode cell. Avertical groove or overflow tube 50 connects with overflow drain tubes56 (see FIG. 4) to guide overflow fuel from the anode to the fuelreservoir 61.

The cathode cell frame 81 is adapted to receive a cathode electrode 23on its face away from the anode cell and positioned at the outside ofthe cell unit so that the cathode is in a position to breathe air. Acathode cell opening is positioned and adapted to receive the cathodeelectrode and to form a cell or reservoir which may for example, beaqueous potassium hydrazine or other electrolyte. Above the cellopenings are recessed electrolyte feed openings through whichelectrolyte may be added to place the cell in condition for operating orto replenish electrolyte during operation.

The cathode electrode 23 comprises catalytic material formed intoelectrode shape and structure and having conductive leads 25 extendingtherefrom, and the anode, according to one preferred embodiment of theinvention, similarly comprises a catalytic material formed intoelectrode shape and structure and having lead 24 extending therefrom.Thecathode is formed of a catalytic metal which is capable of receivinga source of oxygen such as air and transforming it into a usefuloxidizing source within the electrolyte. A suitable cathode is disclosedand claimed in co-pending application Ser. No. 687,562 filed Dec. 4,1967 now abandoned. The anode may be a catalytic member such asdisclosed and claimed in co-pending application filed on or about June2, I970 and entitled RANEY METAL SHEET MATERIAL, Ser. No. 43,220 now US.Pat. No. 3,637,437 or the above-identified copending application Ser.No. 687,562 filed Dec. 4, 1967, now abandoned. In addition, othermethods may be employed to form either a cathode or anode.

It has been found that catalytic silver is a presently preferredelectrode for the cathode and for one presently preferred embodiment ofthe anode according to the present invention. Catalytic silver may beformed into an electrode in any of several methods. For example, analloy of the catalytic metal such as silver with a chemically activemetal (capable of being easily leached out of an alloy) such as aluminummay be formed into a desired shape either alone or supported on asubstrate such as preferably a wire screen. The chemically active metalthen is leached out of the structure, to form in effect, a Raney metalcatalyst such as Raney silver. Such electrode formation is disclosed andclaimed in co-pending application Ser. No. 687,562 filed Dec. 4, 1967,now abandoned, and in the aboveidentified application filed on or aboutJune 2, 1970 entitled RANEY METAL SHEET MATERIAL Ser. No. 43,220, nowUS. Pat. No. 3,637,437. According to another method of forming anelectrode, a silver compound from which the non-silver elements can bepartly or largely removed is formed into electrode shape optionally witha supporting member included therein such as a wire screen or the like.For example, silver carbonate or certain other silver salts can beformed into the shape of an electrode and heated to bring about thermaldecomposition, desirably in the presence of a reducing agent. If such aprocedure is employed, it is preferred to employ as the reducing agentthe fuel which ultimately is to be employed in the fuel cells. Thus,decomposition of silver carbonate to form a catalytic electrode for thepresent cell is advantageously accomplished in the presence of a smallquantity of hydrazine.

In addition to these methods of preparing a cathode or an anode, theremay be employed a specially prepared catalytic silver powder which canthen be formed into an electrode by coating on a substrate surface,pressing, compacting or otherwise treating the formed electrode to causeit to be self-supporting under operating conditions. Depending on thedesired use of the electrode, there may be employed a porous resinbinder such as for example, a polyfluoro resin such as for example,Teflon. Resins such as hexafluoropropylene, chlorotrifluorothylene andinterpolymers thereof are typical of the class of resins which arepresently preferred, although generally speaking, there may be employedany resin porous to air and capable of retaining the aqueous electrolytewithout leaking.

Illustratively, commercially available silver carbonate is mixed with asolution of roughly equal parts of acetic acid and water. This mix isstirred until foaming stops. Thereafter, hydrazine hydrate (64 percenthydrazine) is added with stirring until finally, the silver particlessettle to the bottom of the container. The silver is washed to removehydrazine and is oven dried at 180 to 200 C. The product is highlycatalytically active silver particles which appear porous under a highpower microscope.

In another method, silver is prepared from commercially available silvernitrate. In a laboratory scale operation, grams of silver nitrate isdissolved in I25 ml. of distilled water. Fifty milliliters of aceticacid is added slowly with stirring and hydrazine hydrate is addeddropwise. A white foam builds up very quickly with the addition of about10 ml. of the hydrazine mixture. The hydrazine hydrate is added untilthe mixture is creamy and smooth and then the entire contents stirredinto a large quantity of water. Additional hydrazine is added untilsilver is deposited as powder in the bottom of the container. Thisrequires a total of about 20 ml. of hydrazine hydrate. The silver in thebottom of the container is then washed to remove hydrazine and ovendried at about to 200C.

A similar procedure can be followed starting with commercially availablesilver powder which is washed or dissolved in a suitable material andthen treated with hydrazine hydrate.

To form a cathode from the silver powder as thus prepared, the powder isplaced on a layer of powder of polyfluoro resin and pressed and heated.For example, a layer of about 1 inch thick of duPont 2B Teflon powder isspread over an area of 100 square centimeters. On top of this powder isplaced a uniform layer of 30 grams of silver powder. The layered powdersare pressed at 9,000 lbs. per 100 square centimeters at 325 C. for 15minutes. The pressed layer is then held flat with a light weight andallowed to cool. It is then put in a press at 100,000 lbs. per I00square centimeters. To complete the formation of a suitable cathode forthe I00-watt fuel cell, conductive leads such as nickel wire are securedto the flat electrode body. If

desired, an electrode in this manner can be employed as an anode as wellas a cathode; it is preferred, however, to employ a somewhat differentelectrode as anode.

An anode can be prepared of the same silver powder prepared by any ofthe above described methods. ln a preferred procedure, a supportmaterial such as a metallic screen, preferably nickel, is employed as ameans to supply a conductive support base. To prepare an anode of 100square centimeters area, grams of the silver powder is spread out in alayer on a suitable metallic support. The 100 square centimeters metalscreen is then placed on this layer and an additional 15 grams of silverpowder is spread out on top of the screen. All the layers, of course,should be as uniform as possible. The assembly comprising a metal screenwith silver powder both above and below is then pressed in a die andshaped at 200,000 lbs. per 100 square centimeters at room temperature.It is then pressed without the die at 50,000 lbs. per 100 squarecentimeters at 450 for 10 minutes. Conductive leads are attached,preferably prior to pressing.

According to another preferred embodiment of the invention, there may beemployed an anode which is not noted for its catalytic properties. Forexample, a porous nickel anode has been used with surprising success. Apressed and sintered catalytic silver powder anode on a nickel meshsupport has yielded a current flow of up to 8 amperes or more per 100square centimeters for a long period of time, and can yield a currentflow of up to about 4 amperes per 100 square centimeters virtuallyindefinitely without polarization. Under like conditions, a porousnickel anode not specially treated to produce catalytic properties hasyielded a current flow up to about 5 amperes per 100 square centimetersvirtually indefinitely. Other anode electrodes, according to thisinvention, showing good properties are porous stainless steel, porousnoble metals such as palladium, platinum or the like, and other porousmetals resistant to chemical attach by the highly caustic electrolyteand made from metals higher in the electromotive series than hydrogen.

It is presently believed that the anode 22 must be porous in theembodiments illustrated in FIG. 2 and H6. 5, at least for the reasonthat the fuel is supplied behind the anode electrode. The fuel is thendecomposed as it penetrates the anode and comes to the electrolytesurface.

1 claim:

1. A fuel cell comprising a cell block having end walls and a bottomwall forming outer walls of a fuel chamber and an electrolyte chamber,an anode electrode mounted on said block in position to separate thefuel chamber from the electrolyte chamber, and forming a common internalwall of the fuel chamber and the electrolyte chamber, means to supply anaqueous electrolyte to said electrolyte chamber, means to circulate aliquid fuel to and recirculate said fuel from the fuel chamber, saidfuel circulation means including a fuel input means at the top of thefuel chamber, fuel discharge means at one end of the fuel chamber todischarge fuel from the fuel chamber, and a downwardly inclined fueldirecting baffle positioned below the fuel input means to receive fuelby gravity flow from the fuel input means and to direct fuel downwardlyand toward the other end of the fuel chamber away from the fueldischarge means, causing the fuel to flow in a circular path within thefuel chamber over substantially the entire surface of said anode, anexternal side wall mounted on said block to form an external wall ofsaid fuel chamber, and an air breathing cathode defining an externalwall of said electrolyte chamber and positioned with one face thereof incontact with said electrolyte and another face thereof facing externallyfrom said cell block.

2. A fuel cell as set forth in claim 1, wherein said cathode comprisescatalytically active silver and an airporous resin.

3. A fuel cell as set forth in claim 2, wherein said anode electrode isa porous electrode of catalytically active silver powder formed into anelectrode structure.

4. A multi-cell fuel cell comprising a multiplicity of pairs ofindividual cells according to claim 1, said individual cells beingmounted in pairs, said cells in each pair being mounted face to face,with the cathode electrodes being outwardly facing in each pair.

1. A fuel cell comprising a cell block having end walls and a bottomwall forming outer walls of a fuel chamber and an electrolyte chamber,an anode electrode mounted on said block in position to separate thefuel chamber from the electrolyte chamber, and forming a common internalwall of the fuel chamber and the electrolyte chamber, means to supply anaqueous electrolyte to said electrolyte chamber, means to circulate aliquid fuel to and recirculate said fuel from the fuel chamber, saidfuel circulation means including a fuel input means at the top of thefuel chamber, fuel discharge means at one end of the fuel chamber todischarge fuel from the fuel chamber, and a downwardly inclined fueldirecting baffle positioned below the fuel input means to receive fuelby gravity flow from the fuel input means and to direct fuel downwardlyand toward the other end of the fuel chamber away from the fueldischarge means, causing the fuel to flow in a circular path within thefuel chamber over substantially the entire surface of said anode, anexternal side wall mounted on said block to form an external wall ofsaid fuel chamber, and an air breathing cathode defining an externalwall of said electrolyte chamber and positioned with one face thereof incontact with said electrolyte and another face thereof facing externallyfrom said cell block.
 2. A fuel cell as set forth in claim 1, whereinsaid cathode comprises catalytically active silver and an air-porousresin.
 3. A fuel cell as set forth in claim 2, wherein said anodeelectrode is a porous electrode of catalytically active silver powderformed into an electrode structure.